draw_main.c

Description

draw_main.c is a source code file from the bpdemo application that contains all the core drawing and rendering logic. It is not a standalone command-line tool. This file is responsible for translating the numerical state of the beam pattern simulation into the graphical representations displayed in the various windows of the GUI.

It uses a set of custom drawing functions (prefixed with jX_) to render lines, rectangles, and polygons onto off-screen pixmaps, which are then copied to the screen.

Functionality

void draw_main(jX_win_param *DA, int type)

This is the primary rendering function. It is called whenever a part of the GUI needs to be redrawn. It checks which drawing area (DA) it is being asked to draw and what type of display is requested, then executes the appropriate drawing code.

• If Drawing Area is DA_main:
  • This is the main visualization window.
  • It sets the coordinate system and clears the background.
  • It draws the individual transducer elements at the bottom.
  • It can draw the beam pattern in polar coordinates (if the “log BP” toggle is on).
  • It can draw the individual wavefronts as “wiggles” arriving at the array (if the “wiggles” toggle is on).
  • It draws a line indicating the current beam steering angle.
• If Drawing Area is DA_polar:
  • This window displays the phasor diagrams.
  • It can draw the individual phasor vector for each element.
  • It can draw the vector sum of all phasors.
  • It can display the final amplitude as a bar graph.
  • The exact visualization depends on the state of the toggle buttons in its popup menu (pt_sum, pt_indiv, pt_amplitude).
• If Drawing Area is DA_time:
  • This window displays the time-domain view of the signals.
  • It draws the sinusoidal wave received at each element over time, clearly showing the phase shifts between them.
• If Drawing Area is DA_options:
  • This section appears to be a placeholder, as it only fills the area with a solid red color.

void expose_main(jX_win_param *DA)

This is a helper function called by the event handlers when an Expose event occurs. Its only job is to copy the pre-rendered image from the off-screen pixmap (where draw_main does its work) to the visible window on the screen. This double-buffering technique ensures smooth, flicker-free updates and animations.